Among the 150 people feared dead are three Americans, including a northern Virginia woman and her daughter.

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A Germanwings co-pilot is believed to have deliberately crashed his plane into a mountain in the French Alps on Tuesday, killing 150 people, including a woman and her mother from northern Virginia and an American man reportedly living in Barcelona.

Germanwings flight 4U 9525 was less than an hour into its route from Barcelona to Dusseldorf when co-pilot Andreas Lubitz, alone in the cockpit, locked the pilot out of the cockpit and crashed it, officials said Thursday. He apparently wanted to “destroy the plane,” a prosecutor said.

1: Number of crew members in the cockpit when the Germanwings jet crashed.

2: Number of crew members required in the cockpit at all times on United States airlines' flights. When one pilot uses the restroom, a flight attendant takes the pilot's place in the cockpit temporarily. Many international carriers, Lufthansa's Germanwings among them, have no such protocol.

1: Number of black boxes so far recovered. Investigators have retrieved cockpit voice recordings from it that led them to believe the co-pilot had deliberately crashed the plane.

About 58,300: The number of flight hours the aircraft accumulated since it was delivered to Lufthansa in 1991.

1953: The year an Air France plane crashed near the site of the Germanwings crash, near the town of Barcelonette, killing 49 people.

50,000: The number of euros Lufthansa will pay, as a preliminary payment, to the relatives of each deceased passenger to help cover immediate costs, a company spokesperson told NBC News. The money will not have to be paid back, Lufthansa said.

400: Number of French officers mobilized for the plane crash, according to the French National Gendarmerie.